Biological effects of D2O administration to Coturnix japonica

Levels of 7.8, 18.5 and 26 mole % deuterium oxide were administered sequentially to $\text{Coturnix japonica}$ (Japanese quail) via the drinking water. The primary effect observed was on egg frequency, which decreased from a normal level of 0.89 for 7.8 mole % D₂O to a low of 0.38 during the administration of 26 mole % D₂O. Adverse symptoms, such as hyperexcitability, convulsions, skin ulcerations, comatosity, weight loss, or death, which have been associated with deuterium toxicity in other animals, were not observed in these experiments. The amount of deuterium deposited in the water of the egg was 6.9, 13.98, and 19.83 mole % when 7.8, 18.5 and 26 mole % deuterium respectively was administered. For each period, the deuterium content of egg water rapidly reached a maximum concentration after which the concentration decreased slightly. This dilution effect has not been noted previously in body fluids from other animals.     

Procedure and Analysis of a Useful Method in Determining Mycelial Dry Weights from Agar Plates

The evaluation of growth by dry weight determination of fungus mycelium for agar plates was examined. The data obtained were statistically analyzed. This method was shown to be sufficiently accurate to be used as an investigative tool.     

Physiological characteristics of NG2-expressing glial cells

Antibodies against the chondroitin sulfate proteoglycan NG2 label a subpopulation of glial cells within the CNS, which have a small cell body and thin radiating processes. Physiological recordings from these small cells in acute brain slices have revealed that they possess unique properties, suggesting that they may comprise a class of glial cells distinct from astrocytes, oligodendrocytes, or microglia. NG2-expressing glial cells (abbreviated as “NG2 cells” here) have a moderate input resistance and are not dye- or tracer-coupled to adjacent cells. They express voltage-gated Na⁺, K⁺and Ca²⁺conductances, though they do not exhibit regenerative Na⁺or Ca²⁺action potentials due to the much larger K⁺conductances present. In addition to voltage-gated conductances, they express receptors for various neurotransmitters. In the hippocampus, AMPA and GABA_Areceptors on these cells are activated by release of transmitter from neurons at defined synaptic junctions that are formed with CA3 pyramidal neurons and GABAergic interneurons. These rapid forms of neuron-glial communication may regulate the proliferation rate of NG2 cells or their development into mature oligodendrocytes. These depolarizing inputs may also trigger the release of neuroactive substances from NG2 cells, providing feedback regulation of signaling at neuronal synapses. Although the presence of Ca²⁺permeable AMPA receptors provides a pathway to link neuronal activity to Ca²⁺dependent processes within the NG2 cells, these receptors also put these cells at risk for glutamate-associated excitotoxicity. This vulnerability to the sustained elevation of glutamate may underlie ischemic induced damage to white matter tracts and contribute to cerebral palsy in premature infants.     

Multimeric bivalent immunogens from recombinant tetanus toxin H<Subscript>C</Subscript> fragment,synthetic hexasaccharides,and a glycopeptide adjuvant

Using recombinant tetanus toxin H_C fragment (rTT-H_C) as carrier, we prepared multimeric bivalent immunogens featuring the synthetic hexasaccharide fragment of O-PS of Vibrio cholerae O:1, serotype Ogawa, in combination with either the synthetic hexasaccharide fragment of O-PS of Vibrio cholerae O:1, serotype Inaba, or a synthetic disaccharide tetrapeptide peptidoglycan fragment as adjuvant. The conjugation reaction was effected by squaric acid chemistry and monitored in virtually real time by SELDI-TOF MS. In this way, we could prepare well-defined immunogens with predictable carbohydrate–carrier ratio, whose molecular mass and the amount of each saccharide attached could be independently determined. The ability to prepare such neoglycoconjugates opens unprecedented possibilities for preparation of conjugate vaccines for bacterial diseases from synthetic carbohydrates.     

Relationships among pure cultured strains of Frankia based on host specificity

Fifty strains of Frankia were tested for their ability to nodulate six species of actinorhizal plants. Pure cultured strains were used to inoculate seedlings of Alnus glutinosa (L.) Gaertn., Alnus rubra Bong., Casuarina equisetifolia L., Elaeagnus angustifolia L., Hippophaë rhamnoides L. and Myrica cerifera L. in nutrient solution culture. From the results of this study, host inoculation groups among the actinorhizal plants were defined. Although overlap between host inoculation groups appears to be common, the results from this study did not support the view that Frankia strains are promiscuous. All Frankia strains tested in this study could easily be classified into four major host-specificity groups.     

Contribution à la connaissance de la faune parasitaire d' Argentine,XV. Etude morphologique de Heteroxynema (Cavioxyura) viscaciae n. sp. (Nematoda,Heteroxynematidae) parasite de Lagidium viscacia boxi (Mammalia,Rodentia)

Résumé Heteroxynema (Cavioxyura) viscaciae n. sp., parasite du caecum et du gros intestin d'un rongeur caviomorphe d' Argentine, Lagidium viscacia boxi Thomas, est décrit. Cette nouvelle espèce est très proche de Heteroxynema (Cavioxyura) chiliensis Quentin, 1975, parasite d' Octodon degus (Molina) au Chili, dont elle se distingue essentiellement par ses mensurations et par la disposition de certaines papilles génitales des mâles. L'étude de cette nouvelle espèce montre l'existence: (i) au niveau des structures buccales d'un dimorphisme sexuel d'un type peu fréquent chez les Oxyuroidea; (ii) de quatre paires seulement de papilles génitales mâles voisinant avec des reliefs cuticulaires qui, dans d'autres espèces, ont peut-être été confondus avec des terminaisons nerveuses supplémentaires; (iii) d'un gubernaculum et d'un spicule, organes rarement observés chez les Heteroxynematidae, mais dont la présence dans d'autres espèces du groupe pourrait avoir été ignorée; (iv) au niveau de l'ovéjecteur, d'un sphincter particulièrement différencié et développé.

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Heteroxynema (Cavioxyura) viscaciae n. sp., parasitic in the caecum and large intestine of Lagidium viscacia boxi Thomas, is described. The most closely related species is Heteroxynema (Cavioxyura) chiliensis Quentin, 1975, a parasite of Octodon degus (Molina) from Chile, from which the new species differs by its measurements and disposition of the male's genital papillae. Study of this new species shows the existence of: (i) a type of sexual dimorphism infrequent in the Oxyuroidea, at the level of the buccal structures; (ii) only four pairs of male genital papillae adjoining cuticular protuberances which in other species may have been confused with supplementary nerve endings; (iii) a gubernaculum and a spicule, structures infrequently observed in the Heteroxynematidae, and possibly overlooked or ignored in other species; (iv) a sphincter which is strongly differentiated and developed.

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Resumen Se describe a Heteroxynema (Cavioxyura) viscaciae n. sp. paràsito del ciego intestino grueso del rodeor Lagidium viscacia boxi Thomas. Esta nueva especie se asemeja a Heteroxynema (Cavioxyura) chiliensis Quentin, 1975, paràsito de Octodon degus (Molina) de Chile de la cual se diferencie esencialmente por sus medidas y por la disposicion de las papilas genitales del macho. El estudio de esta nueva especie muestra la existencia de: (i) un tipo poco frecuente en los Oxyuroidea de dimorfismo sexual a nivel de las estructuras bucales; (ii) cuatro pares de papilas genitales en el macho ubicadas proximas a relieves cuticulares que en otras especies pueden haber sido confundidos con terminaciones nerviosas suplementarias; (iii) de un gubernàculo y una espicula, organos raramente observables en los Heteroxynematidae, pero cuya presencia en otras especies del grupo pudo haber sido ignorada; (iv) de un sphincter particularmente diferenciado y desarollado.

     

Digitalis receptor sugar binding site characteristics: A model based upon studies of Na+, K+-ATPase preparations with differing digitalis sensitivities

The structure-activity relationships of the genin moieties of digitalis glycosides are commonly elucidated by determining the inhibitory potency of a variety of genins toward the plasma membrane Na⁺, K⁺-ATPase; qualitatively these relationships appear to be fairly independent of the specific Na⁺, K⁺-ATPase preparation utilized for the analysis. To determine whether this is the case with regard to the sugar moieties of glycosides, the inhibitory effects of 12 monoglycosides of digitoxigenin toward four Na⁺, K⁺-ATPase preparations of different origin were measured. It was found that while recognition of the major structural determinants of sugar activity appeared to be independent of enzyme source, recognition of the minor structural determinants of activity showed some source dependence. It was also observed that the intrinsic sensitivity to sugar potentiation may be source dependent and unrelated to intrinsic sensitivity to inhibition by digitoxigenin. These observations are compatible with a model of the Na⁺, K⁺-ATPase sugar binding site(s) in which intrinsic sensitivity to sugar attachment as well as recognition characteristics (for sugar structural features) both determine the extent to which a sugar moiety may contribute to the activity of monoglycosides. Further, in these studies one of the Na⁺, K⁺-ATPase preparations employed was obtained from rat brain, a tissue known to contain a mixture of ouabain sensitive and insensitive isoforms. We have observed that the rigorous purification techniques employed appear to have selectively removed from or denatured the less ouabain sensitive al isoform found in this enzyme preparation.     

The effect of salinity on the composition of fatty acid double-bond isomers andsn-1/sn-2 positional distribution in membrane phospholipids of a moderately halophilic eubacterium

We report the first study of the effect of NaCl on the double-bond isomeric composition of fatty acids and theirsn-1/sn-2 positional distribution in the membrane phospholipids of a moderately halophilic eubacterium. The major phospholipids, phosphatidylethanolamine and phosphatidylglycerol, ofVibrio costicola grown in 1M or 3M NaCl both have ansn-1 saturated,sn-2 unsaturated distribution of fatty acids. There is a greater effect of salinity on the fatty acid composition of phosphatidylglycerol compared with phosphatidylethanolamine. The fatty acids in phosphatidylethanolamine of cultures grown in 1M compared with 3M NaCl have the same unsaturation index and average chain length, but different double-bond isomeric compositions. In comparison, the fatty acid composition of phosphatidylglycerol is more unsaturated, with a different double-bond isomeric distribution, and has a shorter average chain length in cultures grown in 3M compared with 1M NaCl. The pattern of fatty acid isomers of 16:1 and 18:1 shows thatV. costicola uses the anaerobic pathway of fatty acid biosynthesis. The presence of the isomers 16:1c11 and 18:1c13 in the phospholipids of cultures grown in 3M but not in 1M NaCl indicates that external salinity affects the specificity of fatty acid synthetase in this moderately halophilic bacterium.     

Current perspectives on plasmodesmata: structure and function

Recent studies on plasmodesmata have shown that these important intercellular passages for communication and transport are much more sophisticated in both structure and regulatory abilities than previously imagined. A complex, but not well understood, substructure has been revealed by a variety of increasingly reliable ultrastructural techniques. Proteinaceous particles are seen within the cytoplasmic sleeve surrounding the desmotubule. Dye-coupling studies have provided experimental evidence for the physical pathway of solute movement, supporting conclusions about substructural dimensions within plasmodesmata drawn from the ultrastructural studies. Calcium has been identified as a major factor in the regulation of intercellular communication via plasmodesmata. Evidence from studies on virus movement through plasmodesmata suggests a direct interaction between virallycoded movement proteins and plasmodesmata in the systemic spread of many viruses. There is increasing evidence, albeit indirect, that in some plant species phloem loading may involve transport of photoassimilate entirely within the symplast from mesophyll cells to the sieve element-companion cell complexes of minor veins.     

Distribution of actinomycetes in near-shore tropical marine sediments

Actinomycetes were isolated from near-shore marine sediments collected at 15 island locations throughout the Bahamas. A total of 289 actinomycete colonies were observed, and all but 6 could be assigned to the suprageneric groups actinoplanetes and streptomycetes. A bimodal distribution in the actinomycete population in relation to depth was recorded, with the maximum numbers occurring in the shallow and deep sampling sites. This distribution can be accounted for by a rapid decrease in streptomycetes and an increase in actinoplanetes with increasing depth and does not conform to the theory that actinomycetes isolated from marine sources are of terrestrial origin. Sixty-three of the isolated actinomycetes were tested for the effects of seawater on growth. Streptomycete growth in nonsaline media was reduced by 39% compared with that in seawater. The actinoplanetes had a near obligate requirement of seawater for growth, and this is presented as evidence that actinomycetes can be physiologically active in the marine environment. Problems encountered with the enumeration of actinomycetes in marine sediments are also discussed.